Dry concentrator



June 23, 1936. LDRHFUS 2,044,775

DRY CONCENTRATOR,

Fi'led Feb. 12, 1934 7 2 Sheets-Sheet l INVENTOR June 23, 1936. E Ln u' 2,044,775

DRY CONCENTRATOR Filed Feb. 12, 1934 2 Sheets-Sheet 2 INVENTOR E.L.D1"eifu/s BY wwmm ATTQRNEY Patented June 23, 1936 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to placer mining, and particularly to the recovery of values from sand and gravel deposits without the use of. water or other liquids.

. The principal object of my invention is to pro.- vide a machine for this purpose which will effectively separate and concentrate the precious and relatively heavy content from a mass of sand and gravel'fed into the machine. From tests made with an-aetual full-sized. machine I have found that I am able to recover practically one hundred per cent of gold andother mineral par.- ticles of any measurable size as well as approximately seventy-five per cent or more of mineral dust or fine values.

The machine may be used with. damp material as Well as dry, and withheavy black sandas well as with the ordinary relatively light sand and gravel. A further object of the invention is to. pro duce a simple and inexpensive device and yet one which will be exceedingly effective forthe purpose for whichit is designed.

These objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

Inthe drawings similar characters of reference indicate corresponding parts in the several views:

Figure 1 is a side elevation of the machine.

Figure 2 is an enlarged fragmentary end view of the same, looking into the values discharge end, and partly broken out to show the air blast separating means. I

Figure 3 is a side View mainly in section of the {separating drum detached.

Figure 4 is a fragmentaryenlarged-horizontal section of the drum at the values discharge end.

Referring now more particularly to the characters of reference on the drawings, the machine comprises an open ended drum I preferably of cylindrical form. This drum is turnably supported on flanged rollers 2 disposed on opposite sides of the drum below its center line and engaging rail bands 3 extending about the drum. These rollers are mounted on shafts 4 journaled on frame beams 5, said shafts and the beams being set at a certain slope to the horizontal base beams 6 of the frame. The drum will therefore have a corresponding slope from end to end, such slope being preferably about 12 /9.

One of the shafts 4 is provided with a sprocket orotherdriving wheel as at I, operatively connected to suitable power drive means .(not

shown), while the two shafts beyond the upper endof the drum are connected by a belt or similar drive 8 so that the rotative action is'imparted to the drum on both sides.

Extending inside thedrum from end to end is a helical flange 9 providing a continuous channel ID of similar form between the turns of the flange. The direction of. the pitch of the helical flange relative to the direction of rotation of the drum is, such that relatively inert matter. in the channel will be gradually conveyed. along the same toward the upper end of the drum. The flange projects inwardly from and. is in unbroken contact with the inner periphery of the drum, and gradually decreases-in depth from the lower end of the drum as plainly shown in Figure. 3, until adjacent the last two turns. or so of the flange, whose. depth then. remains constant, as shown at 90.. Such latter depth, and that of the corresponding portion of the channel, is very shallow or approximately in a full sized machine.

Extending about said flange turns 9a and also about a portion ofaturn of the adjacent flange 9 is a retaining rail l I, supported from the flange at intervals by suitable. brackets 13.. This rail is disposed inwardly of the helical. flange so as to leave a space I? approximately the same depth as the flange 9a itself, and its forward face is flush with the forward edge of the flange, as shown in Figure 4.

Mounted in the drum intermediate its ends and supported on the adjacent portion of the spiral flange is a plurality of deflector or, re.- peller elements l3. These are preferably of L- shape form, with one side. resting on the. flange and the other projecting inwardly of the drum. 'Said elements arev set at an acute angle to the axis of the. drum, with their leading ends relatively advanced, and they. are sufficiently long to extend over a number of turns of the helical flange, as shown in Figure 3.

A downwardly angled material feed chute. 14 projects into the lower end of the drum to deposit into the bottom of the helical channel a few turns from the adjacent end of the drum. The upper end of the said channel, which terminates at the adjacent upper end of the drum as shown in Figure 4 discharges into a substantially V-shaped hopper l which extends about the lower portion of the drum at said end and is mounted in in rigid connection with the frame of the machine.

A discharge opening I 6 at the lower apex of the hopper communicates directly with the top, of

an upwardly sloping conduit H. The wall of the hopper on the low side of the opening projects into and extends part way across the conduit to form a bafile l8 as plainly shown in Figure 2. Beyond the opening some distance, the conduit merges with a downwardly bent chute l9. Ahead of the opening an air nozzle 20 is disposed in the conduit I! in facing relation to the bafrle IS. The nozzle only occupies a relatively small portion of the cross sectional area of the conduit and is connected to an exterior conduit 2| leading to a suitable source of air pressure (not shown) and having a control valve 22 therein.

In operation the loose material to be treated enters the drum through the chute M, where it is deposited in the adjacent portion of the channel l0 and naturally spreads along the same or transversely of the drum somewhat. With the rotation of the drum, such material is carried up the forward side of the drum for a short distance and then falls over and back toward the bottom. This action of course is continuous as long as the drum is rotated, and the agitation thus imparted to the material causes an effective separating action to take place, so that the relatively heavy particles will be gradually sifted to the bottom of the channel while the lighter particles remain on top. Also as is naturally the case with a mass which comprises relatively large and small particles all substantially of the same specific gravity, the small particles work toward the bottom while the large particles remain on top- The finest particles in the material such as the sand, and with it the values which have of course a higher specific gravity than the sand or gravel, therefore gradually work to the bottom of the channel and are conveyed toward the upper end of the drum by the advancing screw action of the helical flange.

The material as fed into the drum is discharged in the channel l0 just ahead of the material which is dropping back after being lifted, so that the fresh material is always deposited in the bottom of the channel. Such dropping material becomes inverted as it drops and is received in the turn of the channel immediately above that in which the material is initially deposited, so that it is out of the way of the latter and there is no chance for values in such material being carried out to the waste before being separated.

At the same time and as the fed material accumulates the light material gradually fills up the turns of the channel between the point of feed and the adjacent end of the drum and works its way over the corresponding turns of the flange to discharge from the drum at said end.

The gravel being a relatively compact mass, and some particles thereof being somewhat heavier than the remainder, such particles have a tendency to work up gradually toward the upper end of the drum with the screw action of the helical flange. The deflector elements l3 are for the purpose of preventing such particles from moving the full length of the drum or beyond said elements. The action of these elements with the rotation of the drum is to move through the relatively inert mass in the bottom of the drum and engage any such large gravel particles as project above the inner periphery of the flange. On account of the angular setting of the elements they will deflect such particles toward the low waste discharge end of the drum.

Since the deflecting action is continuous all the fresh gravel particles of the above character which travel toward the deflecting elements are stopped by contact with the gravel already deflected and must ultimately move back and be discharged from the lower waste end of the drum.

At the same time the deflector elements do not interfere with the necessary advancing movement of the heavy values large and small, and with fine material since the elements extend over the channel I!) in which such material is retained and the latter can thus move under said elements without interference. The heaviest particles of course work into the lower corners of the turns of the channel on the leading side of the adjacent turns of the helical flange.

All this time the tumbling action of the material as initially described is being repeated in every turn of the channel, and as the fine and coarse sand and values (the only remaining elements in the material) are advanced beyond the deflector elements l3, said values will positively sift to and remain in the bottom of the channel, with the fine sand directly above and the coarse sand on top. Since the helical flange continuously decreases in depth, the topmost coarse sand ultimately flows back over the top of the flange and away from the upper end of the drum, leaving only the fine sand and values in the channel to be delivered to the hopper l5.

Any relatively large values such as small nuggets which of course have been retained in and advanced along the channel, might roll back over the top of the flange where it is shallowest, if it were not for the retaining rail H which extends along the full length of this very shallow portion of the flange. The space between this rail and the flange is insufflcient to allow the escape of any such nuggets and yet is of ample size to permit of the escape of overflowing sand. In this manner a minimum quantity of sand is finally retained in the channel for delivery to the hopper and yet all values previously separated from the material are positively trapped.

As the sand and values pass into the conduit ll through the opening l6, they naturally tend to flow down the conduit. The air blast being directed against this downward flow, blows all but the heaviest material up past the hopper opening until it enters the waste chute l9, leaving the heavy values unmolested to flow down the conduit ll into a suitable receptacle. Due to the presence of the baflle [8 the air is prevented from possibly blowing up into the hopper which would prevent the proper discharge therefrom. Since the conduit I1 extends upwardly a certain distance beyond the opening I6 before turning down, any heavy particles which may be initially engaged by the air blast and blown past the opening, have a chance to recover from the influence of the blast and drop back down the conduit ll instead of being discharged into the waste chute I9.

The material is thus subjected to a quadruple effect action between the feed and the final recovery, all of which makes for the success of the machine. First is the initial tumbling action on the bulk of the sand and gravel which at the same time moves the material beyond the point of feed. Then there is the deflecting or repelling of the large light particles of the gravel intermediate the ends of the machine. This is followed by the handling of the fine and coarse sand toward the upper end of the drum, in connection with the retaining of any relatively large values; and finally the ultimate separation of the fine waste material from the values all as above described.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

1. A placer concentrator comprising a drum, means rotatably mounting the drum so that its bottom has an upward slope from end to end, means to feed material into the drum adjacent its lower end, a helical flange extending lengthwise of and about the drum on the inside to form a channel into which the material is fed, and arranged to advance material in the channel to the upper end of the drum, the uppermost turns of the flange being relatively shallow, and a rail extending about said turns inwardly thereof and radially spaced therefrom sufficient to permit of the escape of small particles from the channel and over the flange.

2. A placer concentrator comprising a drum, means rotatably mounting the drum so that its bottom has an upward slope from end to end, means to feed material into the drum adjacent its lower end, a helical flange extending lengthwise of and about the drum on the inside to form a channel into which the material is fed, the pitch of the flange relative to the direction of rotation of the drum being such that material retained in the channel will be conveyed to the upper end of the drum deflector elements mounted directly on and extending over a number of adjacent turns of the flange intermediate the ends of the drum, said elements extending inwardly from the flange and being set at a forward acute angle to the axis 20 of the drum.

ERNEST L. DREIFUS. 

